Modulation in a transmitting apparatus for digital broadcast (for example, terrestrial digital broadcast in Japan) first maps a bit stream of a transmitting signal onto a complex plane through a mapping process. For example, in 64QAM (Quadrature Amplitude Modulation), a bit stream of a transmitting signal is segmented every 6 bits and mapped to 64 signal points on a complex plane.
Furthermore, in OFDM (Orthogonal Frequency-Division Multiplexing), the data (signal) mapped to 64 signal points on a complex plane is subjected to the IFFT (Inverse Fast Fourier Transform). Then, the digital signal having been subjected to the IFFT is converted to an analog signal, and then up-converted to a desired frequency and transmitted from an antenna.
On the other hand, demodulation in a receiving apparatus for terrestrial digital broadcast implements the opposite process to the above-described modulation. That is to say, an analog signal received by an antenna is converted to a digital signal, and furthermore, in OFDM, subjected to the FFT (Fast Fourier Transform) and propagation path compensation.
Then, the signal after propagation path compensation is subjected to error correction and decoding and output as a TS (Transform Stream) format signal, and a video/audio signal is output by decoding this TS signal. As described above, for example, although the Fourier Transform is used in a receiving apparatus for terrestrial digital broadcast, it is known that the optimal position of the time window in the Fourier Transform (the FFT time window position) varies depending on the environment.
However, moving the FFT time window position causes deterioration of propagation path compensation for a certain period of time, resulting in degraded reception performance.
Also, in order to cancel ICI (Inter-Carrier Interference), for example, a propagation path variation value is calculated from the propagation path estimation values of earlier and later symbols upon calculation of ICI, but phase rotation is occurred for propagation path estimation values if the FFT time window position is changed.
In this way, when finding a propagation path variation value from propagation path estimation values of varying FFT time window positions, the propagation path variation value is not calculated correctly, and therefore the accuracy of ICI cancellation deteriorates and reception performance degrades.
Now, various receiving apparatuses for digital broadcast have been proposed heretofore.
In the related art, there have been proposed various kinds of receiving apparatuses for digital broadcast.
Patent Document 1: Japanese Laid-open Patent Publication No. 2004-266814
Patent Document 2: Japanese Laid-open Patent Publication No. 2000-295195
Patent Document 3: Japanese Laid-open Patent Publication No. 2009-278448
Patent Document 4: Japanese Laid-open Patent Publication No. 2010-268177